The present invention relates to a photodetection device for receiving a laser beam projected by rotary irradiation and for measuring an operating position according to photodetecting condition.
In the past, as a representative system for forming a reference plane by projecting a laser beam in rotary irradiation, a system has been known, which comprises a rotary laser system and a photodetection device installed at a measuring point for receiving a laser beam from the rotary laser system.
The rotary laser system projects a laser beam each having a spot-like cross-section by rotary irradiation and forms a reference plane. For instance, by projecting a laser beam within a horizontal plane by rotary irradiation, a horizontal reference plane is formed. By projecting the laser beam within a vertical plane, a vertical reference plane is formed. By projecting the laser beam within a tilted plane, a tilted reference plane is formed.
The photodetection device has a photodetector for receiving and detecting the laser beam. Based on the laser beam detected by the photodetector, a horizontal reference position, a vertical reference position, etc. are measured. Further, when the rotary laser system projects the laser beam in rotary irradiation, the photodetection device detects the laser beam. Based on the result of detection, a distance between the photodetection device and the rotary laser system is measured.
In general, the photodetection device comprises a photodetector with a predetermined length mounted at a predetermined position on a rod-like body. The relation between the photodetection device and the reference plane is detected according to a photodetecting position of the laser beam by the photodetector, and the photodetection device is moved to an adequate position. The photodetection device is erected for installation at a measuring point by an operator. The photodetector receives the laser beam when the operator moves the photodetection device as necessary up and down, for example. Thus, the photodetector must have a certain length.
However, when civil engineering work is carried out for a wider range, a distance between the rotary laser system and the photodetection device will be longer, and the length of the photodetector also will be longer in view of the working efficiency.
In this respect, JP-A-2002-39755 proposes a measuring system, which can detect positional relation between the photodetector and the laser beam only by the photodetection device, which merely comprises a spot-like photodetector.
According to JP-A-2002-39755, a rotary laser system projects a plurality of tilted fan-shaped laser beams by rotary irradiation to facilitate the receiving of the laser beams by the photodetection device, and deviation of the laser beams from a reference position is detected according to time difference caused when the photodetector receives the plurality of fan-shaped laser beams. This makes it possible to perform communication between the photodetection device and the rotary laser system when communication data are superimposed on the laser beams. An amount of deviation and a direction of deviation are transmitted to the photodetection device, and a position of the photodetection device can be accurately adjusted.
However, the invention described in JP-A-2002-39755 is based on the assumption that the photodetection device is held at the vertical position. This means, for example, the system has to be constructed in such manner that a tilt sensor or the like should be provided on the photodetection device side, and that an operator must hold the photodetection device at the vertical position. As a result, the photodetection device must have complicated structure. Also, there are such complicated procedures that the operator must hold the photodetection device at the vertical position while paying attention to the tilt sensor. When a distance is measured by the photodetection device and the rotary laser system, a lower end of the photodetection device acts as a measuring point. When the photodetection device is tilted, there has been such problem that the deviation between the lower end and the photodetection device may directly cause a measurement error.
Further, there has been a problem in that there must be provided measuring means separately for the measurement of the distance between the rotary laser system and the photodetection device.